Biological healing of a tissue opening commences through the proximity of the opposed living tissue surfaces. If the opening is very large or if its location subjects the wound to continual movement, a physician will seek to forcibly hold the sides of the opening in close proximity so as to promote the healing process.
Human skin tissue is comprised of three distinct layers of tissue. The epidermal layer, also known as the epidermis, is the outermost layer and includes non-living tissue cells. The dermal layer, or dermis, is the middle layer directly below the epidermal layer and comprises the living tissue of the skin that is the strongest of the three layers. The subcutaneous, or hypodermis layer is the bottom layer of skin tissue and includes less connective tissue making this the weakest layer of skin tissue. Healing occurs best when the opposing dermal layers of the skin tissue are held in proximity with each other.
While traditional suturing remains a popular method of effectuating closure of wound openings, the use of staples and staplers as a closure technique has become increasingly popular, especially in surgical settings where the opening is created through a purposeful incision. In these settings, the incision tends to make a clean, straight cut with the opposing sides of the incision having consistent and non-jagged surfaces.
Prior art methods of closing tissue using a stapler require at least two hands. For example, when stapling a skin opening, a medical professional typically uses one hand to manually approximate the opposing sides of the skin opening while another hand is used to position the stapler so that a metal staple will span the opening. The stapler is then manipulated such that the staple is driven into the skin with one leg being driven into each side of the skin and the cross-member of the staple extending across the opening external to the skin surface. Generally, the legs of a metal staple are driven into an anvil causing the metal staple to deform so as to retain the skin tissue in a compressed manner within the staple. This process can be repeated along the length of the wound opening such that the entire incision or wound is held closed during the healing process.
While effective in holding an incision or wound closed, conventional metal staples unfortunately require removal after the healing process of a wound opening is completed. As the sciences of medical and materials technology have advanced over the course of the past century, new bioabsorbable polymers and copolymers have been developed that provide medical professionals with an alternative to metal staples that must be removed. Fasteners made of bioabsorbable materials, sometimes referred to as bioabsorbable or biodegradable, break down or degrade over time in the body, with the residuals being either absorbed or ultimately expelled by the body's natural processes.
Bioabsorbable polymer fasteners are preferable to metal staples because they do not have to be removed. While there has been active development of dermal layer suturing techniques, little has been done in the area of staples and staplers for use in connection with the dermal layer. In a series of patents issued to Green et al., including U.S. Pat. Nos. 5,292,326, 5,389,102, 5,489,287 and 5,573,541, a subcuticular stapling method and apparatus are disclosed that were ultimately commercialized as the U.S. Surgical SQS Subcuticular Stapling Apparatus. The Green et al., patents describe a stapling technique employing a handheld apparatus with jaws to proximate, interdigitate and overlap opposing sides of dermal layer tissue along the length of a skin opening. The apparatus then drives a single spike through the interdigitated and overlapped dermal layers of the opposing skin surfaces in order to secure both sides of the dermal tissue on the single spike. The trigger assembly for this apparatus utilizes a conventional reciprocating trigger arrangement whereby the direction of squeezing action of the trigger is generally parallel to and opposite of the direction in which the spike is ejected from the fastener. Although this technique reduced the time required to effectuate a subcuticular skin closure, the SQS device was not commercially successful in part because the resulting closure produced an undesirable wave-like scar that sometimes did not heal effectively.
A novel bilateral approach to fastening dermal tissue using bioabsorbable fasteners is disclosed and described in U.S. Pat. No. 6,726,705, as well as in U.S. patent application Ser. Nos. 10/448,838, 10/607,497 and 10/603,397, to Peterson et al, all of which are commonly assigned to the assignee of the present application and all of which are incorporated by reference in their entirety. In one embodiment, this bilateral approach to tissue fastening utilizes a first apparatus to manipulate opposed sides of tissue to form target tissue zones followed by a second apparatus that effects a bilateral insertion of a tissue fastener to retain opposed dermal layers across an incision or wound in close approximation to facilitate healing. By maintaining contact of the dermal layers through the healing process, the healing process is enhanced which results in less chance of infection, faster recovery and improved aesthetic appearance. In addition, no subsequent medical follow-up is necessary to remove fasteners as is typically necessary with nonabsorbable fasteners. In this embodiment of Peterson et al., however, two medical practitioners may be required, one for operating each of the two apparatus that are utilized to accomplish bilateral capture and insertion of the bioabsorbable fastener.
While the bilateral tissue fastening methods and apparatus taught by Peterson et al. provide many advantages, there are opportunities to improve upon the principles taught by Peterson et al. with respect to tissue fastening applications. For example, it would be desirable to provide for a fastening device that can be operated more effectively by a single medical practitioner with one hand to repeatedly and accurately approximate tissue while deploying staples.